1. Field of the Invention
The invention relates to rehabilitative exercise, and more particularly to methods and equipment designed to permit an athlete or patient to exercise selected parts of the body under controlled conditions within a prescribed range.
Accidents, athletic injuries, and aging often result in weakness or deterioration of muscles, muscle groups, ligaments and other soft tissue structures impairing the operation of limbs, body parts, and their related extremities. It is well appreciated that muscle impairment can often be reduced or eliminated by appropriate exercise and physical therapy. Athletes and healthy individuals also have the need to strengthen and condition healthy muscles and forestall weakening or injury.
Many exercise procedures and devices have been devised to strengthen, condition and rehabilitate targeted muscles and muscle groups. The effectiveness of these procedures and devices often depends upon frequency, ease of use, and adherence to correct procedures. While the attendance and participation of a trainer, physical therapist or other health care professional is undoubtedly preferred; availability, cost and scheduling frequently dictate that such procedures be performed in private by the athlete or patient.
There are a variety of ways to exercise. The exercise may be isotonic, wherein a muscle shortens against a constant load; it may be isometric involving muscular contraction without movement of the involved parts of the body; or it may be isokinetic and performed with specialized apparatus that provides variable resistance to movement, so that no matter how much effort is exerted the movement takes place at a constant speed.
A muscle's response to the exercise may be concentric contraction, wherein force is generated by muscle contraction sufficient to overcome external resistance and the muscle shortens as it contracts; or it may be eccentric contraction, wherein the force generated by muscle contraction is insufficient to overcome the external resistance placed on the muscle and the muscle fibers lengthen as the muscle contracts.
2. Description of Related Art
Numerous devices have been developed to exercise the foot, ankle and lower leg. For example: U.S. Pat. No. 5,100,129 to Porter and Spence; U.S. Pat. No. 5,186,658 to Masson and Masson; U.S. Pat. No. 6,390,957 to Knight; and U.S. Pat. No. 6,540,651 to Aberton et al, each employ elastic tensioning devices for connecting a foot to a rigid structure. U.S. Pat. No. 4,605,220 to Troxel; U.S. Pat. No. 6,063,013 to Vathappallil; U.S. Pat. No. 6,277,057 to Hayden; and U.S. Pat. No. 6,821,235 to Johnson and Johnson describe foot engaging devices including springs or shock absorbers to control movement of a foot within a prescribed range and with controlled pressure.
The value and versatility of elastic connecting members, is demonstrated by the disclosures of U.S. Pat. No. 5,016,874 to Boardman, U.S. Pat. No. 6,942,487 to Corbalis; U.S. Pat. No. 6,554,747 to Rempe; and U.S. Pat. No. 7,214,171 to Thelen and Thelen. Boardman shows a bar connected by four elastic members to the corners of a portable square planar frame. Corbalis uses a spring board suspended by flexible straps within a frame to teach skate board tricks. Rempe discloses a housing within which a person can be suspended while performing functional tasks and exercises. Thelen et. al. suggests the use of a bungee-type cord to train figure skaters.
The use of elastic tensioning for wrist and hand exercising is disclosed in U.S. Pat. No. 6,099,438 to Dawson, wherein springs support a hand grip within various plastic tubing structures.
To a greater or lesser extent, exercise techniques and devices, act to encourage or restrain the motion of the joints being exercised. The “motion of the joints” may be described as the motion of the limb extremity distal to the joint. The joints themselves, under the restraints and control of their structure and related muscles and ligaments, permit or constrain movement of the limb extremity within the three cardinal body planes: the sagittal plane being the median plane of the body (or any plane parallel thereto), the transverse plane being transverse to the anterior-posterior axis of the body, and the frontal plane being parallel to the main axis of the body and at right angles to the sagittal plane.
Motion occurs in the three cardinal body planes, but is defined by the anatomical position of the limb extremity relative to the limb or body as a whole which does not always correspond to the cardinal planes. For example, motion of the ankle/subtalar joint complex—addressed in the preferred embodiment hereinafter described—in the sagittal plane is plantar flexion or dorsiflexion, in the transverse plane is abduction or adduction, and in the frontal plane is inversion or eversion.
The direction of motion of a limb extremity around a joint, constitutes or describes an “axis of motion”. Motion about the joint often involves more than one type of motion and the axis of motion does not fall entirely within one cardinal body plane. It will be appreciated that the axis of motion of a joint is not the same for every individual, but is determined by bone structure, joint structure and ligamentous stability. Indeed, often the axis of motion is not a static axis, but a variable axis that changes both position and angulation as the joint is moved through its range of motion.
To date, no satisfactory method or equipment has been developed for unmonitored use that can be adapted to exercise or rehabilitate the muscles, muscle groups, tendons, and ligaments connecting joints, such as ankles or wrists, by constraining exertion of limb extremities against resistance applied within a prescribed three-dimensioned range of motion specifically tailored to the joint and its structure.